Radial Flux Alternator

ABSTRACT

An energy conversion system includes rotor, stator and shell components configurations for increasing power efficiency and improving replacement and repair efficiency. The system harvests environmental energy for lower power generation and accounts for non-mechanical sources of rotational resistance within the generator.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. application Ser. No.15/138,848, filed Apr. 26, 2016, titled “Radial Flux Alternator”, whichis a continuation of U.S. application Ser. No. 13/415,645, filed Mar. 8,2012, titled “Radial Flux Alternator,” now U.S. Pat. No. 9,331,535, bothof which are incorporated herein by reference in their entirety. U.S.patent application Ser. No. 12/778,586, now U.S. Pat. No. 8,461,730,entitled “Radial Flux Permanent Magnet Alternator With Dielectric StatorBlock” is related to the subject matter described herein, subject tocommon ownership and incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

Efficient dynamo-based production of electrical power in environmentalenergy harvesting and other applications in which the dynamo rotor isdriven at low and variable revolutions per minute. Specific applicationsinclude, by way of example, powering systems aboard unmanned maritimeplatforms and harvesting wind power generation.

Description of the Related Art

Extraction of useful energy from locally available environmental sourcesis becoming vitally important to a wide range of applications, andimmediately so for remote sensing and communications devices formilitary and civilian uses. A common element in all devices that harvestenvironmental energy from kinetic sources such as moving wind or wateris the electrical dynamo, which must be capable of operating without anexternal source of current and therefore typically utilizes permanentmagnets. Numerous electrical dynamo designs exist and are patented. Inparticular, these designs include vertical and horizontal axis windturbines and kinetic power pendulum-type devices which respond to X-Yforces (with respect to the pendulum's rotational axis).

One of the problems associated with high-efficiency, radial flux,permanent magnet alternators is cost of fabrication when the rotor sizeexceeds 5 or 6 inches. The cost of rare earth magnets dominates the costequation today, so any reduction in the cost of other componentspresents opportunities to reduce overall cost.

Accordingly, there is a perpetual need in the alternator (dynamo) artfor improved technical designs which balance intended application, size,costs and other factors to meet efficiency demands.

BRIEF SUMMARY OF THE INVENTION

In a first exemplary embodiment, an energy conversion system includes: acylindrical rotor including a mass and multiple magnets affixed on anouter face thereof; a cylindrical stator including one or moredielectric components wound with copper wire in a predeterminedconfiguration, the cylindrical rotor being placed within the cylindricalstator; a shell component rotatably connected with the cylindricalrotor, wherein the cylindrical rotor and the cylindrical stator arelocated within a circumference of the shell component; and a rotatableshaft for simultaneously rotating the cylindrical rotor and the shellcomponent, the rotatable shaft being placed in the center of thecylindrical rotor.

In a second exemplary embodiment, an energy conversion system includes:a cylindrical rotor including a mass and a round plate with multiplemagnets affixed on the periphery thereof by individual L-brackets eachof which has a short section and a long section, the individualL-brackets being secured to the plate by threading a short sectionthereof through individual openings along the periphery and securing oneof the multiple magnets to the long section of each L-bracket; acylindrical stator including one or more dielectric components woundwith copper wire in a predetermined configuration, the cylindrical rotorbeing placed within the cylindrical stator; and a rotatable shaft forrotating the cylindrical rotor, the rotatable shaft being placed in thecenter of the cylindrical rotor.

In a third exemplary embodiment, an energy conversion system includes: acylindrical rotor including a mass and a round plate with multiplemagnets affixed on the periphery thereof by individual L-brackets eachof which has a short section and a long section, the individualL-brackets being secured to the plate by threading a short sectionthereof through individual openings along the periphery and securing oneof the multiple magnets to the long section of each L-bracket; acylindrical stator including multiple dielectric components each havinga length and width and having notches at a top and bottom of the lengththereof, wherein each of the multiple dielectric components includes apiece of copper wire wound around the length of the component throughthe top and bottom notches, the cylindrical rotor being placed withinthe cylindrical stator; a shell component rotatably connected with thecylindrical rotor, wherein the cylindrical rotor and the cylindricalstator are located within a circumference of the shell component; and arotatable shaft for simultaneously rotating the cylindrical rotor andthe shell, the rotatable shaft being placed in the center of thecylindrical rotor.

BRIEF DESCRIPTION OF THE FIGURES

The following figures are intended to be illustrative of the exemplaryembodiments of the present invention and are to be considered inconjunction with the descriptions provided herein.

FIG. 1 illustrates an energy conversion system in accordance with anexemplary embodiment described in U.S. patent application Ser. No.12/778,586;

FIG. 2 illustrates an energy conversion system rotor in accordance withan exemplary embodiment described in U.S. patent application Ser. No.12/778,586;

FIGS. 3a through 3c illustrate an energy conversion system rotor inaccordance with an exemplary embodiment described herein;

FIGS. 4a and 4b illustrate an energy conversion system stator inaccordance with an exemplary embodiment described herein; and

FIGS. 5a through 5e illustrate an energy conversion system with shellrotor in accordance with an exemplary embodiment described herein.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary energy conversion system 10 in a radial flux configurationis shown in FIG. 1 and includes at least the following components: arotor assembly including rotor 15, magnets 20, shaft 25; stator 30;upper plate 35 (optional); lower plate 40 (optional) and spacers 45(optional). A top view of just the stator portion of the prior artsystem in shown in FIG. 2. The rotor and stator assembly could standalone or, alternatively, be held together with an upper plate 35, lowerplate 40 and spacers 45 formed of non-conductive material, such asfiberglass. In order to avoid the need for metal bolts or screws, theplates can be machined with a groove that matched the circumference ofthe stator so that the stator fits snuggly within the groove. The groovemay also have raised teeth or pins (of nonconductive material) thatinterlock with one or more stator slots to prevent rotation of thestator.

Referring to FIGS. 3a through 3c an alternative rotor design 15′ makesuse of low cost metal and non-metal components to achieve cost savings.A circular steel plate 40′ has rectangular slots 50 cut around theperiphery to accept brackets 55 that will hold magnets 60. The brackets55 are L-shaped with the smaller portion of the L passing through thetop of the circular plate and tilted so that is rest flat against thebottom of the rotor plate. The bracket can then be riveted, welded,screwed or otherwise held in place 65. The advantages of this designinclude cost reduction, strength and easy scalability. No complex shapesor expensive machining is required.

With the design illustrated in FIGS. 3a through 3c , the magnet size,the number of magnets desired, and the diameter of the rotor thendetermine the number of magnets affixed to the rotor.

Referring to FIGS. 4a and 4b , an alternative stator for use with therotor shown in FIGS. 3a through 3c , consists of individual statorblocks 70 that make up individual coils in the construction. Moreparticularly, grooved rectangular blocks allow coil wire 75 to bereadily and quickly wound around them. The individually wound blocks 70are then affixed to non-conducting top and bottom plates (only one plate80 shown) by pins, screws, adhesive or other mechanism (see exemplaryholes 78) for securing to form an alternative circular stator assembly30′.

The alternative rotor and stator designs may be used together to form analternator or individually with other stator and rotor variations, suchas those described in U.S. patent application Ser. No. 12/778,586entitled RADIAL FLUX PERMANENT MAGNET ALTERNATOR WITH DIELECTRIC STATORBLOCK which is incorporate herein by reference. The alternative designsreduce costs because there are no complicated shapes, no time-consumingmachining, and no exotic materials required to build the alternator.Assembly time is minimal and individual components, e.g.,magnets/brackets and/or stator blocks, can be replaced in the field ifrequired. Similar to FIG. 1, the alternative circular stator assemblywould be mounted on non-conductive housing material with bearingsinserted top and bottom for the rotor shaft.

Referring to FIGS. 5a-5e , one or more of the alternator designsdescribed herein or in U.S. patent application Ser. No. 12/778,586, maybenefit from the addition of a rotating shell 100 having inside diameter100 a and outside diameter 100 b. The thickness of the shell isdetermined by structural considerations (larger units requiring morematerial for rigidity and strength) and weight limitations. A practicallower limit is 16 gauge for smaller units. Flux extension as a result ofthickness has been determined to be adequate with 16 gauge material. Theshell 100 rotates with the rotor so that there is no relative motionbetween the rotating shell and the rotor. The shell is formed of aferro-magnetic material such as many alloys of steel, cobalt, chromium(IV) oxide, ferrite, iron, magnetite, neodymium, permalloy, andsamarium-cobalt. The rotating shell functions to pull or extend themagnetic flux through the stator windings at a higher average flux thanif the shell is absent. The rotating shell does not generate eddycurrent and associated Lorentz losses since it is rotating with therotor. Accordingly, the addition of a rotating shell described hereinincreased the power density of the alternators. For optimum powerefficiency, the shell is constructed such that it's inside diameter 100a is as close to the outside diameter 30 b of the stator as possiblewithout contacting the stator. Though the shell as illustrated in FIGS.5a-5c is shown as a continuous piece of material, it is alsocontemplated that the shell could alternatively be formed of individualstrips of material 90 placed opposite of the locations of the magnetsper FIG. 5e . Or as a variation thereto, the shell could be formed so asto have cut-outs 105 in the locations thereon that are oppositenon-magnet portions of the rotor as depicted in FIG. 5d . Thealternatives to the continuous shell result in reduced weight and mayadvantageously take advantage of secondary electromagnetic phenomenasuch as smoothing field flux lines and breaking up eddy flows withinlarger diameter, high current conductors.

In operation, the shell effectively shields the magnetic flux of thepermanent magnets outside the alternator to a level that is nearbackground noise. This is important for a number of reasons. Manyelectronics are sensitive to strong magnetic fields and can be damaged,malfunction, or have skewed readings of sensors. As a result, the shellrotor allows more tightly packed integrated systems in which the bufferbetween the alternator and any sensitive electronics can effectively beeliminated. Further the distance in which the alternator and its housingmust be constructed of dielectric/non-conductive materials is reduced.This simplifies design and reduces cost. For example, without the shell,magnetic flux ½ an inch from the surface can be as high as 1000 gauss.With the shell, at the shell surface it is in the range of 10-15 gauss.

The energy conversion systems described herein are based on the use ofpermanent magnets in what is known as a radial flux configuration. Theconfiguration is brushless and results in much greater swept coil areain the same footprint as an axial-flux design and is well suited to lowrotational speed applications as low as approximately 1 rpm. In aparticular embodiment, various exemplary materials and configurationsinclude neodymium magnets, steel rotor and shaft with an unbalancedmass. One skilled in the art recognizes that the number and spacing ofmagnets is changeable in accordance with optimization parameters.Similarly, rotor material and configuration, e.g., hollow, solid,unbalanced, can also be manipulated in accordance with end userequirements. These variations fall within the scope of the invention.The stators are preferably air-core with copper wiring and dielectricmaterials such as fiberglass. The use of dielectric material reduces oreliminates eddy current drag forces, which otherwise oppose rotation ofthe rotor even when the stator coil circuit is open (no load). Examplesof dielectric materials that are suitable include non-carbon compositessuch as fiberglass/eGlass, phenolic resins, plastics, polycarbonate,wood, 3-D printed plastics (such as glass-reinforced nylon), and glass.

As suggested herein, there are various combinations of rotors (15, 15′),stators (30, 30′) and stator shell 100 configurations and materialsubstitutions that may be implemented in accordance with size, powerrequirements, weight restrictions, material costs. For example, asmaller footprint alternator using the shell and smaller (lessexpensive) magnets could produce the same power output as a largerfootprint alternator with no shell. One skilled in the art recognizesthe trade-offs and advantages resulting from the configurationsdescribed herein.

The exemplary configurations described above result from theidentification and neutralization of detracting forces previouslyoverlooked and insignificant in the generator field. Specifically, forharvesting at low rotational speeds to produce relatively low power,e.g., on the order of watts, the configurations described hereinminimize sources of non-mechanical rotational resistance caused by, forexample, the buildup of eddy currents and cogging forces in ferrous orconductive elements in motion-relative components of a permanent magnetalternator. In theory, the spin-down time for a dynamo should begoverned by the friction in its bearings and with the air. Alow-friction device should have a relatively long spin-down time.However, it can be readily shown that typical generators have very shortspin-down times, even when no electrical load is applied. Laboratoryexperiments and application of theory (Lenz, Maxwell, and Faraday), ledresearchers to the conclusion that these excess forces are the result ofeddy current drag, which is overlooked when a powerful prime mover suchas an internal combustion engine is used. In fact, this eddy currentdrag is a significant source of “friction” and is released in the formof heat in the generator. Utilizing the configurations described herein,the spin down time can be increased from several seconds to severalminutes as a direct result of the application of these principles in theform of dielectric construction materials. This approach is distinctivefrom prior art configurations, even those identified as having a“substantially ironless” stator, as some steel is used to help directthe magnetic fields—resulting in some cogging. The exemplary embodimentsdescribed herein eliminate the presence of iron, conductive, orotherwise magnetically interactive materials from the vicinity of thestator or alternator housing.

To that end, the configurations are constructed to utilize dielectricstructural materials to prevent counter-electromagnetic field (EMF) oreddy currents in certain structural components. This includes thematerials use for the stator block, top and bottom plates, andstructural elements such as legs, and outer housing. The exemplaryconfigurations are able to produce useful voltages at very lowrotational speeds, eliminating the requirements for step-up gearing fromlow-speed, high-torque input (also known as break-out torque), which isfrequently encountered with various “renewable” energy harvestingtechnologies, including: wind turbines, both horizontal and vertical(e.g., Savonius, Darrius); Riverine and tidal current turbines anddrogues; and certain types wave energy conversion (WEC) devices.

Operation at very low rotational speeds offers the following advantages:enables direct 1:1 rotational speed with wind turbines and kineticreaction mass devices (wave energy); reduces or eliminates therequirement for transmissions and gearboxes, which reduces costs andcomplexity and scheduled maintenance requirements while increasingreliability and mean time to failure, which is important in remotemarine applications; reduces or eliminates the requirement for precisionbalancing of the rotor to manage vibration, with cost savings; reduceswear on bearings; relaxes structural considerations due to very highcentrifugal forces of high-speed rotors; generates less mechanicalfriction heating; increases mechanical reliability; reduces eddy currentreaction in the permanent magnets, reducing heating in the magnets andimproving performance and lifetime.

The exemplary system described herein has unlimited applicability. Whileimmediate applications for the technology include remote low powerapplications such as individual ocean buoys in the single digit wattpower output range, the scalability of the technology would allow forpower output up to an in excess of 100 kilowatts. Other potential usesinclude unmanned maritime platforms and remote cellular communicationspower stations. The exemplary embodiment described above generatesoutput power in the range of approximately 2 to 20 watts. The energyconversion system is intended to be a plug-and-play generator whereoutput wires can be connected directly to a power supply, e.g., such asthe payload power supply on a buoy.

The embodiments set forth herein are intended to be exemplary of thedescribed inventive concepts and are in no way intended to limit thescope of the invention thereto. One skilled in the art recognizes thenumerous variations that are inherently contemplated by the invention asdescribed.

1. An alternator comprising: a rotor having alternating magnetic andnon-magnetic portions on an outward facing circumference thereof; ashell component surrounding the outward facing circumference of therotor and having ferromagnetic portions located opposite the magneticportions of the outward facing circumference of the rotor, wherein therotor and the shell component are connected to a rotatable shaft; andone or more dielectric components wound with copper wire located betweenthe rotor and the shell component; wherein the alternator generatespower in a range of 2 to 20 watts when the rotatable shaftsimultaneously rotates the rotor and the shell component at a rate aslow as 1 rpm such that there is no relative motion therebetween.
 2. Thealternator according to claim 1, wherein the magnetic portions of theoutward facing circumference of the rotor are permanent magnets affixedthereto.
 3. The alternator according to claim 2, wherein the permanentmagnets are neodymium magnets.
 4. The alternator according to claim 3,wherein the spacing between the permanent magnets is approximatelyequal.
 5. The alternator according to claim 1, wherein each of the oneor more dielectric components has an air core and, a length and widthand notches at a top and bottom of the length thereof, wherein each ofthe one or more dielectric components includes a piece of copper wirewound around the length of the component through the top and bottomnotches thereof.
 6. The alternator according to claim 5, wherein each ofthe one or more dielectric components is formed of a material selectedfrom the group consisting of: fiberglass, phenolic resin, plastic,polycarbonate, wood, glass-reinforced nylon, and glass.
 7. Thealternator according to claim 1, wherein the ferromagnetic portions ofthe shell component are formed of a material selected from the groupconsisting of: steel, chromium (IV) oxide, ferrite, iron, magnetite,neodymium, permalloy, and samarium-cobalt.
 8. The alternator accordingto claim 7, wherein the ferromagnetic portions of the shell have athickness of at least 16 gauge.
 9. An alternator comprising: a rotorhaving alternating magnetic and non-magnetic portions on an outwardfacing circumference thereof, wherein the spacing between the magneticand non-magnetic portions is approximately equal; a shell componentsurrounding the outward facing circumference of the rotor and havingferromagnetic portions located opposite the magnetic portions of theoutward facing circumference of the rotor, wherein the rotor and theshell component are connected to a single rotatable shaft; and a statorlocated between the rotor and the shell component, wherein the statorremains stationary while the rotor and shell component rotatesimultaneously.
 10. The alternator according to claim 9, wherein themagnetic portions of the outward facing circumference of the rotor arepermanent magnets affixed thereto.
 11. The alternator according to claim10, wherein the permanent magnets are neodymium magnets.
 12. Thealternator according to claim 11, wherein the spacing between thepermanent magnets is approximately equal.
 13. The alternator accordingto claim 9, wherein the stator is form of a dielectric material selectedfrom the group consisting of: fiberglass, phenolic resin, plastic,polycarbonate, wood, glass-reinforced nylon, and glass.
 14. Thealternator according to claim 9, wherein the ferromagnetic portions ofthe shell component are formed of a material selected from the groupconsisting of: steel, chromium (IV) oxide, ferrite, iron, magnetite,neodymium, permalloy, and samarium-cobalt.
 15. The alternator accordingto claim 14, wherein the ferromagnetic portions of the shell have athickness of at least 16 gauge.